As integration scales to the 20nm regime and below, the integrated circuit (IC) design has seen the billion transistor counts. For instance, the latest Pascal GPU using 16nm FinFET technology from Nvidia has 150 billion transistors. As a result, it becomes very challenging to verify those billion-transistor chips and there is an urgent need to develop advanced and parallel simulation technique. On the other hand, the counterfeit ICs have become a major security threat for commercial and mission-critical systems. In addition to the huge economic impacts, they post significant security and safety threats on those systems. The objective of this thesis is to develop new techniques to address above two tough issues encountered in VLSI research: new fast parallel circuit simulation and potential solutions to mitigate the counterfeit IC problem.

To accelerate the circuit simulation, we study several important linear algebra operations in simulation steps, such as sparse matrix-vector multiplication (SpMV), direct linear LU factorization and iterative general minimum residual linear solver. Parallel computing such as general purpose GPU programs are good solutions for improving performance of these operations. We apply GPU for these tasks and attain impressive speedup over traditional or CPU methods. All algorithms and implementations are demonstrated with representative numerical experiments and thorough comparisons among different methods and platforms.

For various types of counterfeit ICs - recycled, remarked, cloned, out-of-spec, and over-produced, we propose a multi-functional on-chip sensor and post-authentication policy for detecting and preventing them. Especially for recycled ICs, we propose two kinds of aging sensors, which are based on electromigration (EM)-induced aging effects and ring oscillator (RO)-based frequency aging effects. These two aging sensors can effectively detect chip usage time for both short and long periods. Simulated results show the advantage of the proposed multi-purpose sensor against the existing on-chip sensors in terms of functionality, detection coverage and usage time estimation range and accuracy.

Garnet-type Li7La3Zr2O12 (LLZO) solid-state electrolytes have excellent ion conductivity and chemical stability and show immense potential for the advancement of next-generation all-solid-state batteries. Gaining an in-depth understanding of the structure-property relationship of LLZO is essentially important to optimize the electrochemical performance of LLZO and enhance its practicality for real-world applications. Transmission electron microscopy (TEM) is a powerful tool for the characterization of the structure, composition, and functional properties; however, it is challenging for LLZO because LLZO is susceptible to electron irradiation and also sensitive to the ambient air. In this study, advanced TEM techniques combined with in situ heating, biasing, and cryogenic cooling setups are employed as an effective approach to enable detailed characterization of the structure and transport properties of LLZO solid-state electrolytes, aiming to solve fundamental scientific questions regarding the phase transformations, grain boundary (GB) structures and compositions, and ionic conduction behaviors of LLZO. The investigation begins with a comparative study on the phase transformation during both sol-gel and solid-state syntheses of LLZO using in situ heating TEM, which identifies distinct phase transition pathways and clarifies the origin of surface amorphization. Subsequently, after careful control of sample preparation and imaging conditions to effectively mitigate electron-beam damage to LLZO, the examination of structures and compositions across the GBs of LLZO is conducted to reveal their impacts on ionic and electronic conductivities. It is found that a slight decrease in oxygen content consistently exists in the LLZO GB region, leading to the accumulation of positive charge affecting the local electrical field around the GB. Furthermore, an innovative technical advancement is achieved by the successful implementation of in situ TEM with operando electrochemical impedance spectroscopy measurements under air-free environments. This approach enables the direct measurement of the ionic conductivity of LLZO with different microstructures and further correlates it to the ion conduction and Li dendrite penetration failure at the Li/LLZO interfaces. Our findings offer valuable insights into the understanding of the structure-property relationship, elucidating the impact of microstructural features on ion transport and electrochemical performance. This work highlights the importance for microstructural engineering and compositional optimization of LLZO solid electrolytes, providing promising implications to the development of solid-state battery technologies.

Platinum-based metallic NPs hold considerable interest due to their applications especially in catalysis. The catalytic performance depends on their morphology, structure, and composition. The response under thermal stimuli remains complex and is not fully elucidated. TEM is an indispensable method for characterizing materials from the atomic level to nanoscale. In situ TEM has enabled unprecedented capabilities for observing the real-time evolution of materials during dynamic processes. This study investigates the thermally induced structural and chemical evolutions of Pt-based NPs with different structures and elemental compositions using in situ TEM. In situ TEM generates massive datasets, necessitating effective tools for data analysis. Image segmentation using machine learning was developed to analyze STEM images and quantify NPs behavior at elevated temperatures.The first NP system investigated is Pt-Ni NPs. We synthesized NPs with two distinct structures. In situ TEM reveals morphological evolution from truncated octahedron to spherical-like isotropic shapes, followed by pancake-like ellipsoid shapes. In situ STEM with EDS mapping shows that solid-solution compositional configuration is retained over a large temperature range, while core-shell NPs undergo irreversible solid-solution transitions through chemical homogenization at elevated temperatures. The study extends to quinary PdCuPtNiCo NPs with core-shell and HEA structures. STEM and EDS mapping examine the crystal structure and mixing patterns. In situ experiments reveal that chemical evolutions during heating are controlled by mass transfer with nearby NPs. Without mass transfer, NPs maintain their solid solution structure; however, mass transfer with background atom clusters or neighboring NPs leads to the formation of Janus structures after heating. Overall, this work provides new scientific knowledge about structural and chemical evolutions of metallic NPs model systems during heat treatment. The obtained knowledge can be used as design principles to extend to other multimetallic systems to improve materials’ performance in real applications.